OpenEuphoria

Re: ESL - math.e - rounding

• Posted by "Juergen Luethje" <j.lue at gmx.de> Aug 04, 2005
• 549 views

Christian Cuvier wrote:

<snip>

> In theory, we need the 4 rounding modes below.

I think we should have all 4 rounding modes in the ESL, shouldn't we?

> And the Intel FP architecture supports them all.
>
> [Quoting from Intel FPU documentation]
>
> Table 4-8. Rounding Modes and Encoding of Rounding Control (RC) Field
>
> --------------------------------------------------------------------
>    Rounding     ! RC Field !      Setting Description
>      Mode       !          !
> ---------------+----------+----------------------------------------
>                 !          ! Rounded result is the closest to the
> Round to       !  00B     ! infinitely precise result. If two values
> nearest (even) !          ! are equally close, the result is the even
>                !          ! value (that is, the one with the
>                !          ! least-significant bit of zero). Default
> ---------------+----------+------------------------------------------
> Round down     !          ! Rounded result is closest to but no greater
> (toward =E2=88=92=E2=88=9E)    !  01B     !than the infinitely precise resu=
> lt.
> ---------------+----------+------------------------------------------
> Round up       !          ! Rounded result is closest to but no less
> (toward +=E2=88=9E)    ! 10B      !than the infinitely precise result.
> ---------------+----------+------------------------------------------
> Round toward   !          ! Rounded result is closest to but no greater
> zero (Truncate)! 11B      ! in absolute value than the infinitely precise
>
>                !          ! result.
> ---------------------------------------------------------------------

Interesting, thanks for the information.
It looks as if this must be programmed by using special FP assembler
instructions. So this is no job for me ...

> Commercial rounding is just rounding up, while scientific calculations
> use round to nearst more often.
>
> CChris

Regards,
   Juergen